The universal mobile telecommunications system (UMTS) is a third generation (3G) mobile telephone technology that is most widely used at present. In the UMTS, after completing decoding of data, a physical layer of a receive end passes a check result and decoded data on to a radio link control (RLC) layer of the receive end through a medium access control (MAC) layer. For an RLC entity in acknowledged mode (AM), if decoding at the physical layer fails, an RLC entity of a transmit end is required to retransmit the data to improve a decoding success rate.
Due to a long time and low efficiency of retransmission at the RLC layer, a high speed packet access (HSPA) technology is further introduced to the UMTS, and a hybrid automatic repeat request (HARQ) is supported at the MAC layer, so that data retransmission efficiency is significantly improved, a retransmission rate at the RLC layer is accordingly reduced, and performance of the UMTS is improved.
However, in the UMTS system, a service that does not support a MAC-layer HARQ and uses an RLC AM entity, such as signaling and a packet-switched (PS) R99 service cannot obtain performance gains brought by an HSPA. Because the service cannot support the HARQ at the MAC layer, correspondingly, a retransmission rate at the RLC layer is higher than a retransmission rate of a service that supports the HARQ at the MAC layer. In addition, because a retransmission time at the RLC layer is relatively long, quality of service (QoS) of a service that does not support the HARQ at the MAC layer is affected.